1. Field of the Invention
The present invention relates to a wire bonding device and a wire bonding method in which the impact load applied on a bonding subject at the time of wire contact detection can be reduced and a highly precise and stable bonding can be achieved by a minute bonding ball diameter while enabling to achieve a high productivity through high-speed bonding.
2. Description of the Related Art
Conventionally, it has been required for a wire bonding device to have a structure in which bonding arms are extended in order to avoid interference between the conveyor/fixing mechanism of the bonding subject. It is to satisfy the needs for expanding the field of bonding aiming at large-scaled bonding subjects and improving productivity. On the other hand, in order to cope with the narrowing intervals of the wire bonding portion of the bonding subject, it has been desired that the shape of the bonding portion be made minute with high precision.
FIG. 5 shows a schematic model block diagram of an example of the wire bonding device of the related art.
A wire bonding device of the related art comprises: a Z-axis base 101 mounted on an XY table (not shown) having a unit which drives in the X and Y directions crossing orthogonal to each other; a bonding arm 103 supported by the Z-axis base 101 via a shaft 102 to be capable of swinging; and a VCM (voice coil motor) 104 for driving the bonding arm 103 in the Z-axis direction. Provided in the bonding arm 103 are an ultrasonic horn 109 having a capillary 108 to which a wire 111 made of a gold wire is inserted and a cut clump 110 for cutting the wire 111. The bonding arm 103 has the length long enough to avoid the interference with the conveyor/fixing mechanism of the semiconductor integrated circuit (not shown) as the bonding subject.
An outline of wire bonding performed by the above-described wire bonding device of the related art will be described below.
First, after forming an initial ball in the tip of the wire 111 extended from the bottom end of the capillary 108, the bonding arm 103 is brought down by the VCM 104 until it comes to be in contact with a first bonding point of the semiconductor integrated circuit. At the time of contact detection when the initial ball comes to be in contact with the semiconductor integrated circuit, the bonding arm 103 is driven at low speed in order to reduce impact load applied on the semiconductor integrated circuit. Subsequently, ultrasonic vibrations generated by an ultrasonic oscillator (not shown) is transmitted to the initial ball via the ultrasonic horn 109 and the capillary 108 while applying a prescribed weight thereto so as to bond the wire 111 to the first bonding point.
After completing bonding at the first bonding point, the capillary 108 is brought up through driving the bonding arm 103 by the VCM 104.
Then, the XY table is moved horizontally to the position over a second bonding point and the wire 111 is pressed to be bonded to the second bonding point in the same manner as that in the first bonding point. Subsequently, the bonding arm 103 is brought up and the wire 111 above the capillary 108 is tightly held by the cut clamp 110 and pulled up. Thereby, the wire 111 is cut at the joint of the second bonding point.
Through the steps as described, wire bonding is performed in the first bonding point and the second bonding point.
However, in the case of using the above-described wire bonding device of the related art, it is likely that the inertia of the bonding arm is increased due to extension of the bonding arm. Thus, the shape and the state of bonding become unstable because of impact load applied at the time of contact detection of the wire to the bonding subject, which may result in deteriorating the bondability. In other words, if the inertia of the bonding arm increases, the impact load applied at the time of the contact detection of the wire to the bonding subject increases, which leads to unstable shape and state of the bonding ball in the first bonding point and unstable crushed shape of the wire and the state in the second bonding point. Thus, there may be a case where the bondability is deteriorated.
Furthermore, it is necessary to reduce the impact load by reducing the dropping speed at the time of contact detection in order to obtain a minute and highly precise bonding shape. Thereby, the productivity is to be deteriorated.
An object of the present invention is to provide a wire bonding device and a wire bonding method in which the impact load applied at the time of contact detection of the wire to the bonding subject can be reduced and a stable and highly precise fabrication of a minute bonding ball can be achieved while enabling to shorten the bonding time.
In order to achieve above mentioned object, a wire bonding device according to present invention for performing wire bonding on a bonding subject by bringing a wire, which is being lead out from a capillary provided in the end portion of an arm supported to be capable of swinging to be in contact with the bonding subject, wherein the arm comprises: a first arm supported by a first shaft to be capable of swinging; and a second arm with a smaller inertia than the first arm having the capillary in its end portion, which is supported to be capable of swinging by a second shaft provided on one end of the first arm.
In the above-described bonding device of the present invention, a second arm having a capillary is supported to be capable of swinging on one end of the first arm supported to be capable of swinging. The inertia of the second arm is smaller than the inertia of the first arm. Therefore, by performing bonding through driving only the second arm at the time of bringing wire to be in contact with the bonding subject, the impact load applied at the time of the contact detection of the wire to the bonding subject can be reduced. As a result, compared to the case where the inertia of the arm is larger, the speed at the time of the contact detection of the wire to the bonding subject can be increased.
Moreover, the wire bonding device according to present invention, further comprising a first driving unit for swinging the first arm and a second driving unit for swinging the second arm.
A wire bonding method according to present invention for performing wire bonding by bringing a wire, which is being lead out from a capillary, to be in contact with a bonding subject by using a wire bonding device comprising an arm having: a first arm supported by a first shaft to be capable of swinging; and a second arm with a smaller inertia than the first arm having the capillary in its end portion, which is supported to be capable of swinging by a second shaft provided on one end of the first arm, the method comprising the steps of: bringing the capillary near the bonding subject by swinging the first arm in the approaching direction which is the direction of the capillary approaching the bonding subject until the wire reaches a prescribed height which is a position right before coming into a contact with the bonding subject; moving the capillary positioned in the height right before the contact by swinging the second arm in the approaching direction so that the wire is moved from the height right before the contact to be in contact with the bonding subject; and pressing the wire being in contact with the bonding subject against the bonding subject by swinging the second arm in the approaching direction in pressing step.
In the above-described wire bonding method of the present invention, the capillary is brought near the bonding subject by swinging the first arm until reaching the height right before coming to be in contact with the bonding subject. Contacting of the wire to the bonding subject and pressurizing of the wire are performed by the second arm with the smaller inertia than that of the first arm. Thus, the impact load applied at the time of contact detection of the wire to the bonding subject can be reduced. Also, compared to the case where the inertia of the arm is larger, the speed at the time of the contact detection of the wire to the bonding subject can be increased.
Moreover, the wire bonding method according to present invention, wherein the wire is bonded to the bonding subject by applying ultrasonic vibrations to the wire in the pressing step.
Furthermore, the wire bonding method according to present invention, further comprising the steps of: after completing the bonding of the wire to the bonding subject, bringing the capillary back to the height right before the contact by swinging the second arm in the direction where the capillary recedes from the bonding subject.